My 2005 Suzuki xl7 won't turn over but headlights work. What is the problem.

Hello, if your battery tests "good" and can handle a load (only by testing can you know this, no matter which battery you are using), then move on to checking cabling to ensure they are secure and free of corrosion. Following this, a test of the starting system is needed. Excessive starter draw may be preventing engine cranking also. Of course, beyond all, make sure the engine actually turns! If the engine is locked up for some unknown reason, surely it will not crank with the starter either.